Aquaponics Aeration

Im planning on buying some trout in the next few days to grow in my aquaponics system, so Im thinking a bit about my oxygen levels.

Toward the end of the trout growing period you have a lot of stuff acting against your trout. Your trout are big and make a lot of waste which depletes oxygen as it breaks down, your trout are big and need lots of oxygen, and your weather is getting warmer,  and warmer water doesnt hold as much gas as colder weather does.

You can test this by opening a warm can of beer, or waiting a few years and watching what happens when the oceans stop absorbing carbon dioxide as they warm up a bit.

Anyway...

I have a tube dumping water from my growbed to my sump.

This much water.

Its not under pressure, but is simply overflowing from the growbed at that height. ie this tubes height regulates the depth of the growbed.

no pressure

The tube stopped a few inches above the water and made some nice splashing and bubbling which I thought was adding some oxygen.

Im probably quite correct in thinking that.

But then I added a tube all the way to the bottom of the tank, and pricked a few holes in the tube just after a narrowing where there was an elbow.

This sucks air into the tube via the Venturi effect.








Apparently, this is because the water experiences higher pressure at the restriction just below the elbow, but then lower pressure when the tube becomes wider again. The result of the low pressure is that it sucks in air.

Which is a little odd.

When you put holes in (or before) the bit thats actually restricted, the holes blow out water.

I know because I checked.

So the result is that oddly enough, air is drawn in and the flow of the water draws it down.

Even more oddly, is that the bubbles dont ever really come out. Some do when the water level is a little low, but these are very small, and not many.

The tube is full of bubbles all in chaos, churning around madly.

It looks like this in real life.

The bubbles enter at the top just where the clear tube starts, and they move all the way to the bottom.

Which is also odd given how gently the water is flowing.





At first I thought they were the same bubbles, but if you block the holes, they clear after a few minutes.

Interesting.

As far as I can tell the air is dissolving.

I have no idea if Im probably quite correct in thinking this.

If gas really does dissolve in water that readily and in that quantity, its no wonder fish can live in the stuff.

I think I just got re-interested in the world.

Perhaps its because I stopped taking all those opiates for my hurty ribs.



120 Things in twenty years  thinks ribs make me less thinky.


[EDIT FROM THE FUTURE - I Thought Id add a link to wikipedias entry on Venturi and now that Ive read it I dont think I have any idea what Im talking about, but what I did clearly works. Im just no longer sure why]

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